It is well known to use fuses in electrical circuits to interrupt the flow of current when there is an overcurrent (i.e., overload current or short circuit) or overload event. Fuses typically include one or more fusible elements (also known as “fusible links”) electrically connected to two end conductors or terminals located at opposite ends of the fuse.
Under normal operation, when the fuse is operating at or near its amp rating, it functions as a conductor. However, if a short circuit or overload condition occurs and persists for more than a short interval of time, the temperature of the fusible element eventually reaches a level that causes a high resistance segment of the fusible element to melt. As a result, a gap is formed and an electric arc established. However, as the arc causes the fusible element to “burn back,” the gap becomes progressively larger. Electrical resistance of the arc eventually reaches such a high level that the arc cannot be sustained and is extinguished. The fuse will have then completely cut off all current flow in the circuit. If arc suppression is inadequate, under some fault current conditions, a fuse may not safely clear an overcurrent or overload event, thereby resulting in damage to circuit components.
One material with arc suppressing characteristics is silicone rubber. Silicone rubber is an elastomer composed of silicone containing silicon together with carbon, hydrogen, and oxygen. Silicone rubber is generally non-reactive, stable, and resistant to extreme environments and temperatures from −55° C. to +300° C. while still maintaining its useful properties. One common type of silicone rubber for use in arc suppression applications is room temperature vulcanizing (RTV) silicone.
Silicone arc suppressors have been formed by applying a free flowing (at room temperature) silicone rubber sealant to a fusible element. This free flowing silicone rubber sealant is then air cured to increase its viscosity such that it hardens into a solid-like state and conforms to the shape of the fusible element.
One disadvantage to such silicone rubber arc suppressors is that there can be inconsistency in the silicone rubber sealant. In this regard, due to ambient air conditions (e.g., humidity), the cure time of a free flowing silicone rubber sealant is increased, potentially causing the silicone rubber to not fully cure. As a result, the silicone rubber arc suppressor may not function as intended during operation of the fuse, thereby causing unpredictable results during an overcurrent or overload event.
Another disadvantage of existing silicone rubber arc suppressors is that cure time for the silicone rubber slows the speed at which a fuse can be manufactured, thereby increasing production costs.
The present invention provides an arc suppressor that overcomes these and other problems associated with existing silicone rubber arc suppressors.